The goals of our series of investigations are to relate the acid-base character of coronary arterial blood to myocardial oxygen consumption. We have developed a fluorometric assay of epicardial oxygen supply-demand. We propose to delineate the physiologic parameters governing myocardial oxygen demand and their influence on the area of an experimental ischemic zone. We propose to describe the ischemic zone biophysically and electrophysiologically. In addition, we plan to explore the character and extent of the peri-ischemic "borderzone." Finally, we hope to evaluate methods for the physiologic and pharmacologic manipulation of myocardial infarct size.